The present invention relates to a method for producing an amino acid by fermentation at high industrial efficiency.
As a direct fermentation method for producing and accumulating L-amino acids directly from saccahride, there have been known methods in which mutant strains derived from wild-type strains of microorganism belonging to the genus Corynebacterium, Brevibacterium, Escherichia, Serratia or Arthrobacter. For example, the following are known as L-amino acid-producing mutants: auxotrophic mutants which require amino acids, etc. (Japanese Published Examined Patent Application No. 10037/1981), mutants which have resistance to amino acid analogs and vitamins (Japanese Published Unexamined Patent Application Nos. 134993/1981 and 44193/1987), mutants which have both auxotrophic mutation and resistance mutation to amino acid analog (Japanese Published Unexamined Patent Application Nos. 31093/1975 and 134993/1981), mutants which have lowered degradability (Japanese Published Unexamined Patent Application No. 273487/1988, and Japanese Published Examined Patent Application No. 48195/1977), and mutants whose aminoacyl t-RNA-synthesizing enzymes have a decreased substrate affinity (Japanese Published Unexamined Patent Application No. 330275/1992).
It has also been known that the production of an amino acid can be improved by using a transformants obtained by transformation with recombinant DNAs carrying genes involved in the biosynthesis of amino acids (Japanese Published Unexamined Patent Application Nos. 893/1983, 12995/1985, 210994/1985, 30693/1985, 195695/1986, 271981/1986, 458/1990 and 42988/1990; Japanese Published Examined Patent Application Nos. 42676/1989, 11960/1993 and 26467/1993).
For producing L-tryptophan, there has been a report that the productivity of the amino acid was improved by giving resistance to aminoquinoline derivatives or to phenothiazine derivatives. (Japanese Published Unexamined Patent Application No. 112795/1992).